Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
h,w=[int(x) for x in input().split()]
c=[]
b=0
for i in range(h):
  C=input()
  b+=C.count("#")
  c.append(C)

dist=[[0]*w for i in range(h)]
dist[0][0]=1
d=deque()
d.append([0,0])

dydx=[[1,0],[0,1],[-1,0],[0,-1]]

while d:
  y,x=d.popleft()
  if y==h-1 and x==w-1:
    break
  for i in range(4):
    ny,nx=y+dydx[i][0],x+dydx[i][1]
    if not(0 <= ny < h) or not(0 <= nx < w) or dist[ny][nx]!=0 or c[ny][nx]=="#":
      continue
    dist[ny][nx]=dist[y][x]+1
    d.append([ny,nx])

if dist[h-1][w-1]==0:
  print(-1)
else:
  ans=h*w-b-dist[h-1][w-1]
  print(ans)